WO2018000946A1 - High-strength corrosion-resistant aluminum-carbon-copper alloy grounding material - Google Patents

Abstract

A high-strength corrosion-resistant aluminum-carbon-copper alloy grounding material, including the following components in percentage by mass: 46％-62％ of aluminum, 2％-8％ of copper, 1％-30％ of carbon, impurities: iron <1.5％, silicon <1.5％, and others <1.0％. The corrosion resistance and grounding conductivity of the material are equivalent to those of pure copper. The addition of a carbon particle component improves the hardness and strength of the grounding material, the grounding material can be directly implanted in deep soil in bar form and used directly as a vertical ground, and the alloy has good soil corrosion resistance.

Description

High-strength and corrosion-resistant aluminum carbon copper alloy grounding material Technical field

The invention belongs to the technical field of electrical materials, and is a grounding material for a grounding network (body) of a power system, and particularly relates to a grounding material of aluminum carbon copper alloy with high strength and corrosion resistance.

Background technique

The power system grounding device is generally composed of a horizontal grounding grid, a vertical grounding pole and a grounding down conductor, and is a necessary facility for ensuring power system equipment and personal safety. The horizontal grounding grid and the grounding down conductor are laid in the trenches of the excavation, and the strength requirements are not high; the vertical grounding poles are hammered into the deep ground, so the material strength is required to be high. At present, the grounding materials mainly use galvanized steel, pure copper, and cladding materials such as copper clad steel.

The main problem of using galvanized steel as the grounding material is that the soil corrosion rate is high. Most of the galvanized steel grounding grids that have been running for 5 to 10 years fail due to severe corrosion, resulting in increased grounding resistance and reduced flow capacity. In the event of lightning or short circuit, it is easy to cause an accident, which reduces the safety and reliability of the operation of the power grid.

Pure copper is a good grounding material, with strong conduction and dispersing ability, good resistance to soil corrosion, and can ensure reliable operation of the grounding grid for more than 30 years. However, due to the large amount of copper buried, it will cause heavy metal pollution in the soil environment. It has been restricted in China's standard Soil Environmental Quality (GB15618).

Patent CN101580909A discloses an aluminum-copper alloy material for a grounding grid. The material is mainly composed of aluminum, copper and rare earth. It comprehensively utilizes the conductivity of copper and the corrosion resistance of aluminum, and reduces the amount of copper embedded in the soil while meeting the requirements for the use of the grounding grid. However, due to its low material strength, it is not easy to penetrate into relatively solid land, so it is not suitable for vertical grounding.

Summary of the invention

One of the objects of the present invention is to provide a high strength and corrosion resistant aluminum carbon copper alloy grounding material, and the second object is to provide a method for preparing a high strength and corrosion resistant aluminum carbon copper alloy grounding material.

In order to achieve the above object, the present invention adopts the following technical solutions:

A high-strength corrosion-resistant grounding material having a mass percentage composition of: aluminum 46% to 62%, copper 2% to 8%, carbon 1% to 8%, impurities: iron <1.5%, impurity: silicon <1.5%, The total content of other impurities is <1.0%.

Preferably, the carbon has a particle size of from 2,000 mesh to 8,000 mesh (i.e., a particle diameter of from 1.5 μm to 6.5 μm).

Preferably, the carbon is selected from the group consisting of carbon powder or/and flake graphite powder.

The preparation method of the above high-strength corrosion-resistant grounding material: heating and melting the aluminum ingot, pressing into the copper-aluminum intermediate alloy, copper-aluminum-carbon powder intermediate alloy or copper-carbon powder intermediate alloy according to the ratio, raising the furnace temperature to melt The intermediate alloy in the pool is fully melted and Stir the slag, then sample and test the adjusted components, refine, cool down to the pouring temperature, add one or two of the carbon powder or flake graphite powder according to the ratio of the specified content, or after pre-mixing with copper or aluminum powder. The mixed powder of carbon powder or flake graphite powder is stirred and melted, and then cast into an aluminum carbon copper alloy ingot; the aluminum carbon copper alloy ingot is processed into a product shape suitable for the grounding grid.

Preferably, the pouring temperature is 700 to 800 °C.

Preferably, the processing mode is a forward hot extrusion process, and the heating temperature of the aluminum carbon copper alloy ingot in the forward hot extrusion process is 430-500 ° C.

Preferably, the aluminum ingot is heated and melted in a crucible of an intermediate frequency induction melting apparatus.

Preferably, the copper-aluminum intermediate alloy is pressed using a graphite bell jar.

Preferably, the temperature is lowered to the pouring temperature and kept warm. Advantages: The purpose of heat preservation is to make the melt temperature in the crucible uniform, and the holding time is related to many factors such as the heat preservation performance of the furnace body, the frequency of the intermediate frequency furnace, and the amount of melting.

Preferably: casting into an aluminum carbon copper alloy ingot using a forced cooling mold.

Preferably, the aluminum carbon copper alloy ingot is processed into a rod having a diameter of 50 mm and a length of 2 m.

The high-strength corrosion-resistant grounding material prepared by the above method.

Aluminum is a good conductor material, but the corrosion products Al ₂ O ₃ and Al(OH) _{3 in the} soil are poorly conductive, causing an increase in contact resistance with the soil, so they are generally not used as a grounding material. Adding an appropriate amount of copper (2wt.% to 5wt.%) to aluminum, the composition of the corrosion product is changed to copper aluminum alloy oxide (Al ₂ CuO ₄ ) and its hydrated oxide, thereby reducing the grounding resistance of the corrosion product and improving Grounding performance. However, its strength is low, and when the copper content is 3%, σ _0.2 ≈ 160 MPa. Further increase in the copper content can increase the strength, but the molding processability is deteriorated, and cracking is easy at the time of extrusion or rolling.

The alloy of the present invention is distributed in that the use of copper ensures that the alloy has good electrical conductivity and soil corrosion resistance, and the fine carbon particle component insoluble in the alloy is added, and the particle reinforcing effect is utilized, without affecting the processing property, The amplitude increases the material strength (σ _0.2 ≥ 320 MPa).

Compared with the prior art, the aluminum carbon copper alloy material of the present invention has corrosion resistance and grounding conductivity comparable to that of pure copper. Due to the addition of carbon particles, the hardness and strength of the grounding material are greatly improved. It can be directly used as a vertical grounding electrode in the form of a bar, and the alloy has good soil corrosion resistance.

detailed description

The invention is further illustrated by the following examples.

Example 1

A corrosion-resistant grounding material, the mass percentage of each component is: copper 2.5%, carbon powder 7.0%, iron 0.8%, silicon 1.0%, and the balance is aluminum.

Smelting aluminum carbon copper alloy ingot: the aluminum ingot is placed in the crucible of the medium frequency induction melting equipment, heated to 690 ° C and heated, and after the aluminum ingot is completely melted, the aluminum copper intermediate alloy is pressed into the aluminum alloy according to the above ratio. The temperature is raised to 780 ° C, the molten pool is fully melted, the slag is stirred, the components are sampled and the copper component is adjusted, and then refined, cooled to the pouring temperature, and pressed into the toner block with a graphite bell according to the ratio of the specified content ( The 2000-mesh carbon powder is pre-developed into a block body, fully stirred and melted, and then cast into an aluminum carbon-copper alloy ingot, the pouring temperature is 710-750 ° C, and then the aluminum carbon-copper alloy ingot is forward-extruded. The method is pressed into a bar having a diameter of 50 mm and a length of 2 m. The extrusion barrel is heated at a temperature of 450 to 500 °C.

The prepared aluminum carbon copper alloy bar was processed into a D30 mm×4 mm sample with the same size pure aluminum or pure copper grounding material, and the alkaline soil was buried in the laboratory for accelerated corrosion test. When the soil temperature is 60.0 ° C and the soil water content is kept at 20%, the total soil salt content is 18%, and the soil pH is 8.5 to 9.5. After 360 hours of high-temperature, high-water content laboratory accelerated test, the contact resistance of three grounding material samples and soil was measured dynamically. After 360 hours, the contact resistance of the pure copper sample to the soil was 37.2 Ω, the contact resistance of the aluminum carbon copper alloy sample to the soil was 39.33 Ω, and the contact resistance of the pure aluminum sample to the soil was 210.2 Ω. The corrosion weight loss of the three material samples was calculated by weighing. The corrosion loss of the pure copper material is 251.7 mg, the corrosion weight loss of the pure aluminum material is 87.5 mg, and the corrosion weight loss of the aluminum carbon copper alloy material of the invention is 135.8 mg.

The aluminum carbon-copper alloy material bar of the present invention was subjected to a tensile test on a universal testing machine, and the yield strength measured by the three groups of five-fold samples was σ _0.2 = 373 MPa on average.

Example 2

A corrosion-resistant grounding material, the mass percentage of each component is: copper 7.5%, flake graphite powder 3.0%, iron 0.8%, silicon 1.0%, and the balance is aluminum.

Precast copper-flake graphite powder intermediate alloy block: According to the formulation ratio of the material, 300 mesh pure copper powder and 2000 mesh flake graphite powder are taken, mechanically stirred uniformly, and then ground and mixed in a planetary ball mill with a water cooling system. The tank and sphere of the ball mill are all alumina ceramic materials. After vacuuming to 10 ^-1 Pa, argon gas was charged, the temperature of the tank was controlled below 50 ° C, and the steel was ground at 200 r / min for 1 h, and then taken out into a mold and pressed to a density of 4.0 kg / m ³ ~ 6.5 kg / m ³ The cylindrical block with a diameter of D30mm×30mm is reserved.

Smelting aluminum carbon copper alloy ingot: the aluminum ingot is placed in the crucible of the medium frequency induction melting equipment, heated to 690 ° C and kept warm. After the aluminum ingot is completely melted, the copper-scaly graphite powder is pressed into the graphite bell jar according to the above ratio. The intermediate alloy block is heated to 780 ° C. After it is fully melted in the molten pool, the slag is stirred, then sampled and adjusted to adjust the copper composition, refined, cooled to a pouring temperature of 710-750 ° C, fully stirred and melted, and then cast into aluminum carbon copper. Alloy ingots. Then, the aluminum carbon copper alloy ingot was pressed into a bar having a diameter of 50 mm and a length of 2 m by a forward extrusion method. The extrusion barrel is heated at a temperature of 450 to 500 °C.

Performance data

Test conditions and other comparative material data Referring to Example 1, the contact resistance of the aluminum carbon copper alloy sample to the soil was 35.03 Ω, and the corrosion weight loss was 143.5 mg. The average value of the yield strength measured by the three sets of 5 times samples was σ _0.2 = 351 MPa.

Example 3

A corrosion-resistant grounding material, the mass percentage of each component is: copper 3.0%, carbon powder 1.5%, iron 0.8%, silicon 1.0%, and the balance is aluminum.

Precast copper-aluminum-carbon powder intermediate alloy block: According to the formulation ratio of the material, take 300 mesh pure copper powder, 300 mesh pure aluminum powder and 2000 mesh carbon powder with the same weight as pure copper powder, mechanically stir and evenly put into the belt. Grinding and mixing in a planetary ball mill with a water cooling system. The tank and sphere of the ball mill are all alumina ceramic materials. After vacuuming to 10 ^-1 Pa, argon gas was charged, and the temperature of the tank was controlled below 50 ° C. After grinding at 200 r / min for 1 h, it was taken out into a mold and pressed to a density of 3.5 kg / m ³ to 5.0 kg / m ³ The cylindrical block with a diameter of D30mm×30mm is reserved.

Smelting aluminum carbon copper alloy ingot: the aluminum ingot is placed in the crucible of the medium frequency induction melting equipment, heated to 690 ° C and kept warm. After the aluminum ingot is completely melted, the copper bell-aluminum-carbon is pressed into the copper bell according to the above ratio. The powder intermediate alloy block is heated to 780 ° C. After the material in the molten pool is fully melted, the slag is stirred, and then the sample is adjusted to adjust the copper composition, refined, and cooled to a pouring temperature of 710-750 ° C. After thorough melting and melting, the furnace is poured. Aluminum-aluminum-carbon alloy ingots. Then, the aluminum carbon copper alloy ingot was pressed into a bar having a diameter of 50 mm and a length of 2 m by a forward extrusion method. The extrusion barrel is heated at a temperature of 450 to 500 °C.

Performance data

Test conditions and other comparative material data Referring to Example 1, the contact resistance of the aluminum-carbon-copper alloy sample to the soil was 36.30 Ω, and the corrosion weight loss was 136.9 mg. The average yield strength measured by three sets of 5 times samples was σ _0.2 = 329 MPa.

The above description of the specific embodiments of the present invention is not intended to limit the scope of the present invention, and those skilled in the art should understand that those skilled in the art can do without creative work on the basis of the technical solutions of the present invention. Various modifications or variations are still within the scope of the invention.

Claims (10)

1. A high-strength corrosion-resistant grounding material characterized by: mass percentage composition: aluminum 46% to 62%, copper 2% to 8%, carbon 1% to 30%, impurity: iron <1.5%, impurity: silicon < 1.5%, the total content of other impurities is <1.0%.
2. A high-strength corrosion-resistant grounding material according to claim 1, wherein said carbon has a particle size of from 2,000 mesh to 8,000 mesh.
3. A high strength corrosion resistant grounding material according to claim 1 wherein said carbon is selected from the group consisting of carbon powder or/and flake graphite powder.
4. The method for preparing a high-strength corrosion-resistant grounding material according to any one of claims 1 to 3, characterized in that: the aluminum ingot is heated and melted, and the copper-aluminum intermediate alloy and the copper-aluminum-carbon powder intermediate alloy are pressed in proportion. Or after the copper-carbon powder intermediate alloy, increase the temperature of the furnace so that the intermediate alloy in the molten pool is fully melted, stir the slag, then sample and test the adjusted components, refine, cool down to the pouring temperature, and add the carbon powder according to the ratio of the specified content. Or one or two of the flake graphite powder, or a mixed powder of carbon powder or flake graphite powder pre-mixed with copper or aluminum powder, stirred and melted, and then cast into an aluminum carbon copper alloy ingot; The carbon-copper alloy ingot is processed into a product shape suitable for the grounding grid.
5. The method for preparing a high-strength corrosion-resistant grounding material according to claim 4, wherein the pouring temperature is 700 to 800 °C.
6. A method for preparing a high-strength corrosion-resistant grounding material according to claim 4, wherein the ingot is processed by a forward hot extrusion process.
7. The method for preparing a high-strength corrosion-resistant grounding material according to claim 6, wherein the heating temperature of the forward hot extrusion process is 430 to 500 °C.
8. A method for preparing a high-strength corrosion-resistant grounding material according to claim 4, wherein the aluminum carbon-copper alloy ingot is cast using a forced cooling mold.
9. A method for preparing a high-strength corrosion-resistant grounding material according to claim 4, wherein the aluminum carbon copper alloy ingot is processed into a bar having a diameter of 50 mm and a length of 2 m.
10. A high-strength corrosion-resistant grounding material prepared by the method for preparing a high-strength corrosion-resistant grounding material according to claim 4.